Hack Wilson, 56, 1930
In 1930 major league teams scored 5.55 runs per game, still the highest mark since 1900, and the entire National League hit .303/.360/.448. Wilson, a barrel-chested slugger who stood just 5'6", had already led the NL in homers three times from 1926 to '28 and in RBIs in '29 with an NL-record 159. He didn't hit his first homer of 1930 until the Cubs' seventh game of the year, and had a mere four in April, but he was nonetheless picking up ribbies with alarming frequency.
Through June, he was hitting .341/.444/.705 with 22 homers and 73 RBIs in 69 games, picked up 11 homers and 31 RBIs in July and then had his biggest month in August, with 13 home runs and 53 RBIs; he passed Klein's NL mark of 43 homers in late August and on Sept. 5, he broke his own RBI record. The next day Wilson began a 17-game, 10-homer flurry that carried him to an NL record that stood for 68 years; his RBI record of 190 (later revised to 191) still stands.